1. Field of the Invention
This invention relates to a method of producing integrated circuit apparatus and more particularly, to a method of producing integrated circuit apparatus in which electroconductive interconnection films adjacently disposed having an insulating film sandwiched therebetween are electrically connected with each other via a through-hole formed in the insulating film.
2. Description of the Prior Art
Recently, semiconductor large scale integrated circuits (LSI) are formed in a multilevel interconnection structure in many cases in order to meet the requirements of high density and high speed. The multilevel interconnection structure is formed as follows; First, a first electroconductive interconnection film is formed on a substrate to be patterned, and an interlayer insulating film is formed on the first electroconductive interconnection film thus patterned. Next, after an opening through which an electrical connection is taken therebetween has been formed in the interlayer insulating film, a second electroconductive interconnection film is formed on the interlayer insulating film to be patterned. Also, in the same manner as above, an interlayer insulating film is formed on the second electroconductive film thus patterned, then, an opening is formed in the interlayer insulating film, and a third electroconductive interconnection film is further formed on the interlayer insulating film. As shown above, the multilevel interconnection structure is formed such that an insulating film and an electroconductive interconnection film are laminated alternately on a substrate. The opening formed in the insulating film is called "through-hole", through which the electrical connection is taken between upper and lower electroconductive films.
As the electroconductive interconnection film, a metal film made of aluminum or its alloy has been widely used. On the other hand, as the interlayer insulating film, a silicon oxide film and silicon nitride film have been used in many cases. However, the recent trend is that such an oxygen containing insulating film that is formed of silicon oxide, silicon oxide nitride or the like by, for example, the plasma CVD is mainly used for this purpose. This is because the use of oxygen containing insulating film allows to reduce the stress to be applied to an electroconductive interconnection film as compared with the use of silicon nitride film, so that the stress migration of the electroconductive film can be effectively prevented and at the same time, the dielectric capacity can be reduced to improve the signal transmission speed.
With the multilevel interconnection structure, in order to planarize the surface of a film to be formed, it is general to sandwich a silicon compound layer including silica film between insulating films, or to use a silicon compound such as silicon polyimide incombination therewith. These silicon compounds contain oxygen, so that similar to the case of using silicon oxide or silicon oxide nitride as shown above, the stress-migration of an electroconductive interconnection film can be effectively prevented.
In case of producing a semiconductor integrated circuit apparatus in the above-described multilevel interconnection structure, after perforating a through-hole in an interlayer insulating film formed on a first electroconductive interconnection film, a second electroconductive interconnection film is formed on the interlayer insulating film through the steps or the following processes in order to provide a good ohmic contact between the adjacent electroconductive films;
First, the through-hole is perforated in the interlayer insulating film by an etching method with a photo-resist as the mask, and then, the photo-resist is subjected to a dry/wet treatment to be separated and removed therefrom (through-hole forming process). Next, sputter etching is applied thereto under the vacuum condition thereby removing extraneous materials existing on the surfaces of the interlayer insulating film and the electroconductive interconnection film exposed into the through-hole (extraneous materials removing process). In this case, as an extraneous material to be removed therefrom, there can be pointed out, for example, a metal oxide which is produced by reacting a component of the electroconductive interconnection layer with the oxygen in the air to be adhered onto the surface of the electroconductive film exposed into the through-hole, and a reaction product which is produced in the through-hole forming process to be adhered onto the surface of the electroconductive film and the side surface of the insulating film in the through-hole and residually existed even after the photo-resist removing process.
Subsequently, the second electroconductive interconnection film is formed on the interlayer insulating film thus obtained as above by a sputtering method under the same vacuum condition as applied in the extraneous materials removing process (electroconductive interconnection film forming process). As shown above, the sputter etching process for removing these extraneous materials and the sputtering process for forming the second electroconductive interconnection film are carried out subsequently under the same vacuum condition.
In case of an existing silicon compound layer between insulating films, or in case of a silicon compound layer in combination with the other insulating film(s) and insulating films, by heating the substrate under the same vacuum condition as applied in the electroconductive film forming process, gases including moisture are to be sufficiently removed from the silicon compound layer in advance.
In this case, however, according to the experiments, with the conventional method as shown above, it is found that even if the etching conditions in the through-hole forming process and the sputter etching conditions in the extraneous materials removing process are optimized, the ohmic contact between electroconductive interconnection films becomes disadvantageously unstable, and it cannot be taken at all depending on, for example, the temperature hysteresis occurring thereafter. Why such a problem as shown above is arisen was examined variously and found to occur for the following reasons;
First, when the sputter etching technique is applied thereto in the extraneous materials removing process, molecules of the interlayer insulating film are dissociated from its top surface and/or side surface to be adhered onto the surface of the electroconductive film exposed into the through-hole. In the case of being used an oxygen containing insulating film such as to be made of silicon oxide or silicon oxide nitride, the oxygen dissociated from the insulating film is re-combined with a metal component of the electroconductive film exposed into the through-hole thereby to generate a metal oxide to be adhered onto the surface of the electroconductive film itself. As a result, the extraneous materials thus adhered thereonto hamper the complete interface connection of the adjacent electroconductive films, resulting in unstable ohmic contact between the adjacent interconnection layers.
In addition, if a temperature change is additionally applied thereto while the complete interface connection between the electroconductive films cannot be provided, or if an electric current is applied thereto, the stress-migration and/or electro-migration will be generated at the interface thereof, so that the both of electroconductive films can be completely shielded finally. This means that the ohmic contact cannot be obtained at all between the electroconductive films.
This invention was made in consideration of the above-mentioned disadvantageous situation, and an object of this invention is to provide a method of producing integrated circuit apparatus capable of providing a stable and superior ohmic contact between adjacent electroconductive interconnection films and a good resistance to the stress-migration and electro-migration of the electroconductive interconnection films.